The subject matter of the present invention is a composition for oxidative dyeing of keratin fibers, particularly human hair, which contains at least one alkaline earth peroxide as oxidizing agent or a combination of at least one alkaline earth peroxide and at least one inorganic or organic acid and/or its salt, as well as a method of oxidative dyeing of keratin fibers using the at least one alkaline earth peroxide as oxidizing agent.
Generally either direct-dyeing dye compounds, or oxidative dye compositions which are produced by oxidative coupling of one or more developer ingredients with one or more coupler ingredients, are used for dyeing keratin-containing fibers, for example wool, fur, feathers and especially human hair. Direct-dyeing dye compounds are applied of course under relatively safe conditions, however direct-dyeing dye compounds have only insufficient fastness properties. Usually intense dyeing with good fastness properties may be obtained with oxidative dye compounds. The color of the dyed fiber is developed however under the influence of comparatively strong oxidizing agents, such as hydrogen peroxide, which frequently causes damage to the fiber being dyed. The use of easily dissolved alkali peroxides and alkali hyperoxides as oxidizing agents is described in German Published Patent application DE-OS 44 45 282, however strongly basic and soluble alkali hydroxides, which similarly cause damage to keratin-containing fibers, arise in the vigorous reaction of this peroxide with water. A process for dyeing hair is described in German Published Patent Application DE-OS 36 28 398, in which the coupling reaction is activated so that it runs sufficiently quickly under weakly alkaline reaction conditions by pre-treatment of the fibers with a greatly diluted transition metal salt solution and/or introduction of a reduced amount of transition metal salts in the hair dye composition. Of course the heavy metal ions enter the keratin fibers so that damage to the hair can occur on repeated treatments. A disadvantage of all the above-mentioned oxidizing agents is that they are present at higher concentration at the beginning of their use and these concentrations decrease during the course of the hair treatment.